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Watch Out for the Ouachitas--New Frontier in an Old Area

Richard H. Sams

The Ouachita overthrust belt is a 1,000-mi long trend of Paleozoic rocks lying between the oil prolific Gulf Coast, West Texas, and Mid-Continent regions. Competitive successes from these adjacent regions coupled with the extreme structural complexity of the trend itself have relegated it to a no-man's land position for exploration since the 1930s, yet the few scattered attempts to find oil in these rocks have persistently turned up hydrocarbon shows without a significant discovery until the Isom Springs field was found in 1977.

Capped for the most part by a thin veneer of Cretaceous sediments, geologic windows do occur which display the intensely folded and thrusted Paleozoic sediments beneath. In addition to structural style, these windows have allowed studies of source rocks, thermal maturity, and reservoir quality which reflect encouraging exploratory attributes. Occurrences of shallow oil in immature overlying sediments suggest the possibility of many oil-filled structures below with few breached structures along the trend beneath the thin Cretaceous veneer.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.